Spindle drive

Abstract

The disclosure relates to a spindle drive for a tailgate of a vehicle which can be adjusted between two drive end positions, in particular between a retracted position and an extended position, two drive connections being provided for diverting drive movements and a drive train between the drive connections, the drive train comprising a motor unit and a drive worm gear downstream of the motor unit in drive terms, the drive worm gear having a spindle with an external spindle drive and a spindle nut with an internal spindle nut thread which is in screw engagement with the external spindle thread, a brake assembly being provided for braking at least a part of the drive train of the spindle drive. The brake assembly can be adjustable in relation to its braking action and that the brake assembly is coupled for adjustment thereof with a component of the drive train.

The invention claimed is: 
     
       1. A spindle drive for a tailgate of a motor vehicle configured to be adjusted between two drive end positions comprising a retracted position and an extended position, the spindle drive comprising:
 two drive connections for diverting drive movements,
 a drive train between the two drive connections, the drive train comprising a motor unit and a drive gear, wherein the drive gear is located downstream of the motor unit, such that the motor unit drives the drive gear, the drive gear comprising: 
 a spindle with an external spindle thread, and 
 a spindle nut with an internal spindle nut thread, wherein the internal spindle nut thread is in screw engagement with the external spindle thread, and 
 
 a brake assembly configured to apply a braking force to at least a part of the drive train, 
 wherein the brake force is adjustable and the brake assembly is coupled with a component of the drive train for the adjustment of the braking force, 
 wherein the braking force increases or decreases with the adjustment of the spindle drive over at least a portion of an adjustment range of the spindle drive, and wherein the braking force depends on a position of the spindle drive. 
 
     
     
       2. The spindle drive as claimed in  claim 1 , wherein the brake assembly constantly brakes the drive train. 
     
     
       3. The spindle drive as claimed in  claim 1 , wherein the braking force increases at least over a portion of the adjustment range of the spindle drive with a motorized opening of the tailgate and decreases at least over a portion of the adjustment range of the spindle drive with a motorized closing of the tailgate. 
     
     
       4. The spindle drive as claimed in  claim 3 , wherein the rate of increase and the rate of decrease of the braking force relative to the adjustment of the spindle drive are identical for both adjustment directions of the spindle drive or wherein an increase and decrease of the braking force differs depending on a preceding adjustment of the spindle drive and on an adjustment direction. 
     
     
       5. The spindle drive as claimed in  claim 1 , wherein the brake assembly has an actuating element, wherein the braking force of the brake assembly can be set by an adjustment of the actuating element and the actuating element is coupled with the drive gear in such a manner that the braking force increases or decreases with an adjustment of the spindle drive at least over a portion of the adjustment range of the spindle drive. 
     
     
       6. The spindle drive as claimed in  claim 5 , wherein the brake assembly comprises a brake element and a brake counter-element which are preloaded against each other to generate the braking force via a brake spring assembly and are thereby in frictional engagement with each other. 
     
     
       7. The spindle drive as claimed in  claim 6 , wherein the brake element and the brake counter-element are part of a brake element assembly, wherein the brake element assembly is preloaded via the brake spring assembly to generate the braking force, wherein the brake element assembly has at least two brake elements and at least two brake counter-elements. 
     
     
       8. The spindle drive as claimed in  claim 6 , wherein the actuating element is coupled with the brake spring assembly in such a manner that an adjustment of the actuating element accompanies a change in the preloading of the brake element and the brake counter-element via the brake spring assembly. 
     
     
       9. The spindle drive as claimed in  claim 6 , wherein the brake element is coupled with a component of the drive train. 
     
     
       10. The spindle drive as claimed in  claim 6 , wherein the brake counter-element is coupled with a housing component of the spindle drive. 
     
     
       11. The spindle drive as claimed in  claim 6 , wherein a control gear is provided which has a spindle with an external spindle thread and a spindle nut with an internal spindle nut thread which is in screw engagement with the external spindle thread and wherein the actuating element is coupled with the drive gear via the control gear, wherein the spindle of the drive gear is coupled with the spindle of the control gear, and wherein the actuating element is coupled with the spindle nut of the control gear or forms the spindle nut of the control gear. 
     
     
       12. The spindle drive as claimed in  claim 11 , wherein the control gear comprises at least one freewheel mechanism configured in such a manner that an adjustment of the spindle drive into at least one drive end position results in the control gear freewheeling when a freewheel end region upstream of the respective drive end position is passed through or wherein the control gear comprises two freewheel mechanisms configured in such a manner that an adjustment of the spindle drive into the two drive end positions results in each case in the control gear freewheeling when a freewheel end region upstream of the respective drive end position is passed through. 
     
     
       13. The spindle drive as claimed in  claim 12 , wherein at least one of the freewheel mechanisms is formed such that when a freewheel end region is reached, the spindle nut of the control gear comes out of engagement with the spindle thereof, wherein the spindle of the control gear has fewer threads than the spindle of the drive gear. 
     
     
       14. The spindle drive as claimed in  claim 11 , wherein a spring assembly of the brake assembly is coupled with the actuating element in such a manner that the spring assembly constantly preloads the spindle nut of the control gear into engagement with the spindle of the control gear. 
     
     
       15. The spindle drive as claimed in  claim 11 , wherein the brake spring assembly has a first spring component and a second spring component which act against one another, at least over a portion of the adjustment range of the spindle drive, to generate the preloading of a brake element assembly, wherein a spring force of the first spring component helps to preload the brake element assembly at least over a portion of the adjustment range of the spindle drive and a spring force of the second spring component reduces the preloading of the brake element assembly. 
     
     
       16. The spindle drive as claimed in  claim 15 , wherein a magnitude of the preloading of the brake element assembly results from a difference between the magnitudes of the spring forces of the two spring components. 
     
     
       17. The spindle drive as claimed in  claim 15 , wherein the two spring components are arranged along the longitudinal axis of the spindle drive on opposite sides of the brake element assembly. 
     
     
       18. The spindle drive as claimed in  claim 15 , wherein both spring components of the brake spring assembly apply a force, in opposite directions, on the same element of the brake spring assembly. 
     
     
       19. The spindle drive as claimed in  claim 15 , wherein an axial stop is provided for the brake element assembly and the first spring component exerts a spring force on the brake element assembly in a direction of the axial stop, wherein the second spring component exerts a spring force on the brake element assembly in the opposite direction. 
     
     
       20. The spindle drive as claimed in  claim 15 , wherein the spring force of the first spring component acting on the brake element assembly is constant, irrespective of the adjustment of the spindle drive, at least over a portion of the adjustment range of the spindle drive. 
     
     
       21. The spindle drive as claimed in  claim 15 , wherein the first spring component or the second spring component of the brake spring assembly, for adjustment of the braking force is coupled with the actuating element, wherein the brake spring assembly is in engagement with, or becomes engaged with, the actuating element depending on the adjustment of the spindle drive for setting the braking force. 
     
     
       22. The spindle drive as claimed in  claim 15 , wherein the first spring component or the second spring component of the brake spring assembly, for adjustment of the braking force is coupled with the spindle nut of the control gear, wherein the brake spring assembly is in engagement with, or becomes engaged with the spindle nut of the drive gear depending on the adjustment of the spindle drive for setting the braking force. 
     
     
       23. The spindle drive as claimed in  claim 5 , wherein an adjustment of the spindle drive between the two drive end positions accompanies an adjustment of the actuating element between two actuating element end positions. 
     
     
       24. A tailgate assembly of a motor vehicle with a tailgate and with the spindle drive for the motorized adjustment of the tailgate as claimed in  claim 1 .